A purple, smog-eating skycraper

Minimal environmental impact is all the rage, but two Hong Kong-based designers say that even no-impact structures are insufficient. Skyscrapers could and should actively clean up the air, they say.

Frederick Givens, an architect, and Benny Chow, a specialist in sustainable building design, presented their version of this concept in Issue 2 of the journal Evolo. They call their brainchild the "Indigo Tower." Envisioned for Qingdao, China, a city with particularly bad air quality, the tower would have a skin featuring a nano-coating of titanium dioxide. When smog hits the skin, sunlight would trigger a chemical reaction that would neutralize grease and toxins, with oxygen and water as byproducts.

The building's signal feature is that this chemical cleansing would continue at night. Photovoltaic panels would capture enough energy from the sun to allow the production of indigo light (near the UV portion of the spectrum) during evening hours. The purple light that would let the chemical reactions continue would be visible for miles: "The indigo glow will become symbolic of the cleansing, counteracting the yellow haze that dominates the daytime hours."

The building's proportions and facade are also designed for maximal, er, greenness. The surface, whose texture is supposed to evoke that of the titanium dioxide molecule, has been fashioned to focus and increase wind speed across the skin, wind that would also power turbines. Gardens spaced at regular intervals up the structure would serve as public spaces, and also collect water produced by the chemical reaction.

Givens and Chow say they have developers who are, at the least, "interested in furthering the research."

Rendering by Charley Chloris